In solving the volume root of cubic equation of state, the correct one is ().
选项：

A:

When T=Tc, if P=pc, there are two imaginary roots and one real root, and the real root is the molar volume of gas

B:

When T < Tc, the equation may have one or three real roots

C:

When T=Tc, if p ≠ pc, there is only one real root and two imaginary roots

D:

When T > Tc, a real root is the molar volume of the gas